The present invention relates to a nozzle 5 with at least one opening that can be closed off, and especially to a nozzle for packaging machines, including those that handle liquid products, with a valve body 9 in the form of a piston that moves back and forth between a retracted position wherein it leaves the opening free and an advanced position wherein it completely closes off the opening.
Nozzles of this type are employed in machines for packaging soups, dairy products, stewed fruits, sauces, etc., which may contain pieces of fruit, vegetables, or meat, in containers that are conveyed in rapid sequence along a conveyor that travels below the nozzle opening. Since these products are food, it is extremely important to maintain sanitary conditions, and the nozzles must be regularly sterilized. Furthermore, the environment around the nozzle is fairly aggressive due to acids from the fruit etc. The components of known nozzles are accordingly made out of stainless steel.
Since the products being packaged often come in fairly large pieces and have long fibers that must be trimmed off during the packaging process, the seat between the piston-like valve body and the nozzle opening must be very tight if the pieces are to be trimmed effectively. The piston, due to the tight seat and the expansion that occurs subject to the high temperatures employed during the sterilization process, gets jammed in the opening or in any piston guides 14 that may be present and cannot operate until the temperature drops back to the normal operating range.
This drawback is acceptable as long as the sterilization is carried out when the machine is down for other reasons. Recently, however, machines have been developed that make it desirable to keep the piston operating even during the sterilization process, which is impossible with known designs and materials if the trimming function of the seat is to be maintained.